A syphon (also called as sealed pot) provided between a downcomer and a high-speed layer generally has a function of controlling fluidization of particles from a downcomer to a high-speed layer and a function of preventing high-speed fluid fluidizing through the high-speed layer from drifting into the syphon or the downcomer, i.e., a function of sealing between the downcomer and the high-speed layer (see, for example, Reference 1).
In such syphon, generally, the fluidizing particles are adapted to fall from the downcomer into the syphon by their own weight.
Recent tendency is to supply, for example, a solid reactant to such syphon and cause the solid reactant to conduct chemical reaction through the use of energy such as heat energy of the particles into gasification, resultant produced gas being withdrawn as product gas.
[Reference 1] JP 2002-206717A